The present invention relates to a process for the production of 4-chlorobenzotrichloride (1-chloro-4-(trichloromethyl)benzene).
4-Chlorobenzotrichloride is a valuable intermediate used in the commercial production of herbicides. It is generally prepared from toluene by ring chlorination to 4-chlorotoluene and followed by methyl group chlorination to the desired compound (Kirk-Othmer Encyclopedia of Chemical Technology, Third Ed., Vol. 5, pages 819-836). This method has critical disadvantages, including the disadvantage that undesirable isomers are formed as by-products in the initial ring chlorination. Other methods of preparing 4-chlorobenzotrichloride include a process wherein toluene is first converted to p-toluenesulfonyl chloride with chlorosulfonic acid and this is further chlorinated (U.S. Pat. No. 3,952,065). This method is relatively complex, requires a relatively expensive reagent and also produces undesirable by-product isomers (in the sulfonation step). New, isomer-specific methods of producing 4-chlorobenzotrichloride in an economical manner would be of considerable value.